1. Field of the Invention
The invention relates to a device, in which a user can assume a user posture and which comprises a carrier for carrying at least one electroacoustic transducer, this carrier being made of an acoustically dense material and extending comparatively close to at least one ear of a user who is in the user posture, this carrier having an electroacoustic transducer attached for acoustic reproduction of sound signals for the ear of the user who is in the user posture, this transducer comprising sound-generation means for generating and emitting sound waves.
2. Description of the Related Art
Such a device of the type defined in the opening paragraph is known from, for example, U.S. Pat. No. 4,027,112. The known device is a seat for a motor vehicle, this seat having a headrest for supporting the head of a user whose user posture is a sitting posture. The headrest is for the greater part, formed by a supporting body provided as the carrier and consisting of an acoustically dense material, this supporting body having two recesses which are each located adjacent a supporting zone for the head and which each accommodate an electroacoustic transducer. The two electroacoustic transducers are constructed for an optimum acoustic reproduction of stereo signals, i.e. essentially music signals. Due to their arrangement on the headrest the two electroacoustic transducers are directed with their front sides towards the head of a user who is in a sitting posture but, in order to achieve said optimum reproduction of stereo signals, both transducers radiate sound waves whose intensities are the same as far as possible over an as large as possible angular range. As a result of this, the sound waves radiated by the two transducers not only reach the ears of the user, who is in a sitting posture, and can consequently be heard by the user with a volume set and desired by the user, but can also be heard by other nearby persons, for example, next to or behind the user. Quite frequently, this is annoying to these nearby persons. Moreover, with respect to the known seat, it is to be noted that the transducers arranged in the known seat and intended for an optimum reproduction of stereo signals are not capable of satisfactorily reproducing pure speech-signal sound waves as occur, for example, during hands-free operation of a telecommunication device.
It is an object of the invention to preclude the afore-mentioned situation in a device of the type defined in the opening paragraph, in a simple and economical manner and to provide an improved device of the type defined in the opening paragraph. According to the invention, in order to achieve this object, a device of the type defined in the opening paragraph is characterized in that the transducer is constructed for an optimum acoustic reproduction of speech-signal sound waves and the transducer is equipped with additional means for realizing a distinct directivity for the speech-signal sound waves emitted by said transducer and, as a result of its directivity, the transducer directs the speech-signal sound waves which it emits preferentially to an ear of a user who is in the user posture.
By means of the measures in accordance with the invention, a device is obtained in a simple, cheap and easy to realize manner, on which a user can assume a user posturexe2x80x94such as a sitting posture or a reclining posturexe2x80x94and which guarantees a satisfactory acoustic reproduction of speech and which, in addition, as a result of the radiation of speech-signal sound waves with a high intensity in a very small angular range due to the distinct directivity, provides a particularly well-aimed radiation towards an ear of a user who has assumed a user posture, which has the advantage that a highly satisfactory sound reception is achieved for a user of a device in accordance with the invention without any undesirable sound radiation of speech-signal sound waves in the vicinity of the user, so that hardly any inconvenience is caused to a person near the user. The well-aimed radiation achieved as a result of the distinct directivity further makes it possible for the user of a device, in accordance with the invention to assure, for a reproduction volume setting he has chosen that overhearing by a person near the user is substantially impossible in the case of speech reproduction, which is for example, desirable when confidential information is communicated to the user during a telephone call made with the aid of the transducer accommodated in the product. In a transducer in accordance with the invention, it has proved to be advantageous if the transducer is optimized for the reproduction of speech signals in a frequency range between approximately 500 Hz and 5 kHz.
It is to be noted that from the document European Patent Application 0 368 291 A1 a device, i.e., a seat of a motor vehicle, is known in which an electroacoustic transducer is accommodated in the area of a headrest, this transducer being adapted or constructed particularly for an acoustically correct reproduction of speech-signal sound waves. However, in said known seat, the transducer accommodated in the seat, i.e., in the headrest of this seat, does not comprise additional means for realizing the distinct directivity for the speech-signal sound waves emitted by this transducer, so that this transducer radiates speech-signal sound waves with high intensity not only in a small angular range but in a comparatively large angular range, as a result of which, this known device does not have the advantages of the invention provided by a device in accordance with the invention.
In a device in accordance with the invention having the characteristic features distinct directivity as described above it has proved to be very advantageous if, in addition, the additional means comprises a baffle interposed between the transducer and the acoustic free space, the transducer being connected to the baffle in an acoustically imperforate manner, and the baffle having at least one sound portxe2x80x94which connects the front volume situated in front of the sound generation means to the acoustic free spacexe2x80x94and at least one openingxe2x80x94which connects the back volume situated behind the sound generation means to the acoustic free spacexe2x80x94the baffle delaying the speech-signal sound waves emitted into the free space via the back volume 31 and the at least one opening, with respect to the speech-signal sound waves emitted via the front volume and the at least one sound port, to different extents in different directions. Such an embodiment has proved to be particularly effective and functional in practical tests. A further advantage of such an embodiment of the invention is that the baffle used, in this embodiment can be used at the same time, for mechanically supporting the electroacoustic transducer.
In a device in accordance with the invention having the characteristic features of a baffle as described above the additional means for realizing a distinct directivity for the speech-signal sound waves emitted by the transducer may include, in addition to the baffle, a felt-material configuration which forms an acoustic delay element. However, in a device in accordance with the invention having these characteristic features, it has proved to be very advantageous if, in addition, the additional means comprises a foam-material configuration which constitutes an acoustic delay element, and the foam-material configuration is arranged in the area of the sound path of the speech-signal sound waves emitted into the acoustic free space via the back volume and the at least one opening, and partly encloses the transducer. Such a foam-material configuration has the advantage that by a suitable choice of the structure of the foam material which is used the influence of the propagation time of the speech-signal sound waves by means of the relevant foam material can be adapted very simply and effectively to different requirements and conditions. The choice of the structure of a foam material may concern, for example, the density of a foam material and/or the air permeability of a foam material.
In a device in accordance with the invention having the characteristic features of a foam-material configuration as described above, it has proved to be particularly advantageous if, in addition, the foam-material configuration extends at least up to the at least one opening in the baffle. In this way a higher effectiveness of the foam-material configuration can be achieved.
In a device in accordance with the invention having the characteristic features of the foam-material configuration extending at least up to the at least one opening in the baffle as described above, it has proved to be very advantageous if, in addition, of the foam-material configuration fills the space in the at least one opening up to the carrier. In this way it is achieved that the foam-material configuration is used for filling the space in the at least one opening up to the carrier of the device, which is particularly advantageous if the entire carrier, together with the electroacoustic transducer accommodated therein and the additional means, is covered or upholstered with a cover, for example, a fabric or the like.
In a device in accordance with the invention having the characteristic feature of a foam-material configuration it has further proved to be very advantageous if, in addition, the foam-material configuration is pot-shaped and is accommodated in a correspondingly pot-shaped recess in the carrier, and the transducer is mounted in the pot-shaped foam-material configuration. Such an embodiment is advantageous for simply assembling a transducer already connected to a baffle and a foam-material configuration so as to form an intermediate device, and for simply building this intermediate device into a device in accordance with the invention.
In a device in accordance with the invention having the characteristic feature of a form material configuration it has further proved to be very advantageous if, in addition, the foam-material configuration consists of a single foam-material part. This is advantageous in view of a particularly simple and low-cost construction.
In a device in accordance with the invention having the characteristic features of distinct directivity as defined above it has further proved to be very advantageous if, in addition, the additional means is constituted by a foam-material configuration which comprises at least two foam-material parts having different foam-material structures, and the foam-material parts at least circumferentially enclose the transducer in the area of its back volume and directly adjoin one another pairwise and each directly adjoin the acoustic free space. Such an embodiment is very advantageous because it is particularly simple from a constructional point of view.
In a device in accordance with the invention having the characteristic features a foam-material configuration of at least two foam-material parts, it has proved to be very advantageous if, in addition, one of the foam-material parts consists of an acoustically dense foam material. Such an embodiment has proved to be very favorable in practical tests.
In a device in accordance with the invention having the characteristic feature of a form-material configuration it has further proved to be very advantageous if, in addition, the foam-material configuration consists of open-pore and, if necessary, densified polyurethane. Such an embodiment has also proved to be very advantageous in practical tests.
However, in a device in accordance with the invention having the characteristic feature of form-material configuration it has also proved to be very advantageous if, in addition, the foam-material configuration consists of open-pore and, if necessary, densified polyethylene. Such an embodiment has also proved to be very advantageous in practical tests.
However, it is to be noted that a foam-material configuration can also consist of other materials than those mentioned hereinbefore.
In a device in accordance with the invention having the characteristic features of distinct directive as defined above it has furthermore proved to be very advantageous if, in addition, the device in constructed as a seat. The measures in accordance with the invention have proved to be very advantageous in such a device. It is to be noted that a device in accordance with the invention can be constructed not only as a seat but, for example, as a bed, sofa or couch.
In a device in accordance with the invention having the characteristic features of being designed as a seat it has also proved to be very advantageous if, in addition, the device is constructed as a seat for a motor vehicle. In the case of a device in accordance with the invention constructed as a seat for a motor vehicle, the measures in accordance with the invention are found to be particularly advantageous and attractive to many users.
In a device in accordance with the invention having the characteristic features of distinct directivity as defined above it has further proved to be very advantageous if, in addition, at least one pair of transducers is attached to the carrier, and each of these transducers is equipped with additional means for realizing a distinct directivity for the speech-signal sound waves emitted by said transducer and, as a result of their directivities, one transducer of each pair of transducers directs the speech-signal sound waves which it emits preferentially to one of the two ears of a user who is in the user posture and the other transducer directs the speech-signal sound waves which it emits preferentially to the other one of the two ears of this user. Providing for example, two transducers which each have a distinct directivity has the advantage of a gain in volume and, consequently, a particularly good acoustic speech-signal reception. If required, it is also possible to connect four transducers to the carrier of which each two transducers emit speech-signal sound waves to one ear of a user.
The afore-mentioned aspects as well as further aspects of the invention will be apparent from the embodiments described hereinafter by way of examples and will be elucidated on the basis of these embodiments.